How far can you bike? the cape is 60+ miles long. The good news is there is a bike trail and good road that will take you from one end to the other. Nickerson SP is in the middle and is my choice, but no hookups. Atlantic Oaks and Shady Knoll are popular with those who require hookups, and also mid cape, all of these can be hard to get into.
To avoid using a toad you better pick a small area to explore, the Falmouth area is really nice and has yet another bike trail. You can visit Marthas Vinyard and Nantucket from Falmouth on the ferrys out of Woods Hole, take along the bikes. Not familiar with CG's in that area though.